Merge branch 'sh-fix-issue-59985' into 'master'

Fix stage index migration failing in PostgreSQL 10

Closes #59985

See merge request gitlab-org/gitlab-ce!26972

lib/gitlab/background_migration/migrate_stage_index.rb

@@ -21,8 +21,8 @@ module Gitlab
                   AND stage_idx IS NOT NULL
                 GROUP BY stage_id, stage_idx
             ), indexes AS (
-              SELECT DISTINCT stage_id, last_value(stage_idx)
-                OVER (PARTITION BY stage_id ORDER BY freq ASC) AS index
+              SELECT DISTINCT stage_id, first_value(stage_idx)
+                OVER (PARTITION BY stage_id ORDER BY freq DESC) AS index
                 FROM freqs
             )
 

spec/lib/gitlab/background_migration/migrate_stage_index_spec.rb

@@ -30,6 +30,6 @@ describe Gitlab::BackgroundMigration::MigrateStageIndex, :migration, schema: 201
 
     described_class.new.perform(100, 101)
 
-    expect(stages.all.pluck(:position)).to eq [2, 3]
+    expect(stages.all.order(:id).pluck(:position)).to eq [2, 3]
   end
 end